The present invention relates to a two-dimensional code comprising unit cells arranged in two-dimension for indicating information, methods and an apparatuses for generating, displaying and reading the two-dimensional code.
A conventional two-dimensional code consists of black or white cells arranged in a matrix to indicate data. One of the black and white colors corresponds to one of bit values “0” and “1”, and other of the black and white colors to other of bit values “0” and “1”. After reading the cells, it is possible to digitize easily the read color data to decode it. The information density in the conventional two-dimensional code, however, is no more than two values “0” and “1” per cell.
From the background, it is considered to colorize each cell of a two-dimensional code to increase the information density in each cell. The cell is unit for indicating a piece of information.
As one of conventional methods of increasing the density in each cell, each cell can indicate one of a plurality of colors, such as white, black, red, blue, green. Each color selectively indicated in each cell corresponds to data set thereto.
For example, assuming that each cell can indicate one of different colors which correspond to five data values, it is possible to set one of the five data values to each cell.
When carrying out a reading process to the colorized two-dimensional code, the cells are read out so that which color is set to each of the cells is identified. The identified colors of cells are matched to the corresponding data values, respectively.
In the reading process to the two-dimensional code, it is important to read out precisely the colors of cells. In order to read out securely the colors of cells, an example of conventional two-dimensional codes comprises color samples corresponding to every color of cells and arranged close to the cells. The color sample allows the colors of cells to be securely read out, which is described in Japanese Patent Publication NO. H10-283446.
Japanese Patent Publication NO. 2000-67191 discloses a conventional method of generating a barcode that is an example of colored two-dimensional codes.
The above conventional two-dimensional code remains technical problems described hereinafter that make difficult to put them into practical use.
First problem is that, when recording large volumes of data corresponding many colors on the conventional two-dimensional code in high density, it is difficult to detect the area in which the conventional two-dimensional code itself is located.
Second problem is that, when recording large volumes of data corresponding many colors on the conventional two-dimensional code in high density, errors are prone to occur in determining what color is set to each cell of the conventional two-dimensional code.
These problems cause an increase in the reading out time of the two-dimensional code, and that in the amount of correcting the errors that occur in the color determination process.